Shinobi no Mono is a series of eight jidaigeki (Japanese historical dramas) which were released in Japan over a four year period from 1962 to 1966. The plot of these two films focuses on a ninja named Ishikawa Goemon and his struggle to survive during Japan's warring states period. The films star Ichikawa Raizo (from Sleepy Eyes of Death fame) who plays Ishikawa Goemon.
In the first film, Goemon is caught cheating with his masters wife. So the master forces him to kill the ninja's mortal enemy, the ruthless warlord Oda Nobunaga. I don't wan't to give away the story so I will just say that Goemon's goal of killing Nobunaga continued into the second film. Both films included a lot of kick ass ninja action.
These movies rocked. They included some awesome ninja and samurai action as well as several gruesome episodes such as a ninja getting his ears cut off. The second movie really followed the collapse of the Nobunaga regime and the rise of Hideyoshi. The movies will have more meaning if you have some background in this period of Japanese history. But even if you don't, they are some damn good ninja movies that I highly recommend.